Process for making electrode grade coke

ABSTRACT

A PROCESS FOR PRODUCING ELECTRODE GRADE COKE FROM HIGH SULFUR AND METAL CONTAINING HYDROCARBON RESIDS COMPRISING THE STEPS OF (1) HEATING THE RESID AT 325-375*C. IN THE PRESENCE OF FINELY DIVIDED SODIUM AND UNDER NITROGEN OR HYDROGEN PRESSURE OF ABOUT 1500 P.S.I.G. FOR 1-3 HOURS, (2) WASHING THE SODIUM TREATED MATERIAL WITH WATER AND CO2 AT ELEVATED TEMPERATURE, (3) DEASPHALTING THE WASHED MATERIAL BY AN ALIPHATIC HYDROCARBON EXTRACTION TO YIELD A PERTOLEUM FRACTION LOW IN SULFUR AND METALS, AND (4) COKING SAID PETROLEUM FRACTION TO OBTAIN AN ELECTRODE GRADE COKE.

United States Patent Office 3,781,198 Patented Dec. 25, 1973 3,781,198 PROCESS FOR MAKING ELECTRODE GRADE COKE Raymond Wynkoop, Gladwyne, and Edward M. Kohn,

Philadelphia, Pa., assignors to Sun Research and Development Co., Philadelphia, Pa. No Drawing. Filed Feb. 2, 1972, Ser. No. 223,025 Int. Cl. Cg 9/14, 9/28, 23/02 U.S. Cl. 208-86 4 Claims ABSTRACT OF THE DISCLOSURE LA process for producing electrode grade coke from high sulfur and metal containing hydrocarbon resids comprising the steps of (l) heating the resid at 325375 C. in the presence of finely divided sodium and under nitrogen or hydrogen pressure of about 1500 p.s.i.g. for 1-3 hours, (2) washing the sodium treated material with water and CO at elevated temperature, (3) deasphalting the washed material by an aliphatic hydrocarbon extraction to yield a petroleum fraction low in sulfur and metals, and (4) coking said petroleum fraction to obtain an electrode grade coke.

It is known in the art that coke for use as electrodes must be free of sulfur and metallic contaminants such as nickel, vanadium, and other metals. There are numerous methods disclosed for treating coke to remove these contaminants. For example, U.S. Pat. 2,878,163 (Hutchings, assigned to the Pure Oil Company and'issued Mar. 17, 1959) discloses a method whereby molten alkali metal hydroxides are used to form a metal or semi-fluid mixture with sulfurized coke and thereby .desulfurize the coke material. U.S. Pat. 3,214,346 (Mason et al., assigned to Esso [Research and Engineering, issued Oct. 26, 1965) discloses a means of oxidizing coke particles with air at low temperature to increase the porosity and surface area of the coke and then the coke is extracted with aqueous alkali metal hydroxide of aqueous hydrogen chloride.

It is also known as disclosed in U.S. Pat. 3,393,978 (Murphy et al., assigned to Carbon Company, issued July 23, 1968) that the amount of sulfur and metals in solid carbonaceous materials, such as coal, char, and coke can be reduced by treating with an alkali metal hydroxide, oxide, carbide, carbonate, or hydride in a fluid bed with steam at a temperature above the melting point of the alkali metal hydroxide and thereafter washing the treated material with water to remove soluble substances therefrom and further treating the washed material with an aqueous solution of a water soluble organic acid.

However, all of the prior art methods suffer from one or more disadvantages, and are particularly diflicult and expensive to handle because of the intractable nature of the coke toward processing.

It has now been found, in accord with this invention, that a metallurgical coke essentially free of sulfur and contaminating metals is readily obtained without treatment of the intractable coke material, but, rather, the coke is prepared from a hydrocarbon resid previously treated by a special method. Thus, in accord with the invention, a process is provided for producing electrode grade coke from a high sulfur and metal containing hydrocarbon resid which comprises the steps of (1) heating the resid at 325375 C. in the presence of finely divided sodium and under nitrogen or hydrogen pressure of from about 500 to about 1500 p.s.i.g. for 1-3 hours, (2) washing the sodium treated material with water and CO at elevated temperature, preferably about 250 C., (3) deasphalting the washed material by a lower aliphatic hydrocarbon extraction to yield a petroleum extract low in sulfur and metals, and (4) coking the petroleum extract to obtain an electrode grade coke.

The hydrocarbon residual material useful in the invention may be selected from any of the petroleum resids normally obtained in refinery operations, but the invention is particularly useful with those resids normally high in sulfur and contaminating metals. Thus, for example, the process of the invention is of significant value with vacuum tower bottoms from Lagomedio crudes, Kuwait residua, residua from Boscan, Lagunillas, Tia Juana, Sunnyland, Sunoco Falls, and the like.

In the first step of the process, the crude bottoms are mixed in a stirred autoclave with finely divided sodium. The average size of the sodium particles is preferably less than about 10 microns, as this will provide adequate particle size for reaction to occur in reasonable time. The mixture of crude and sodium particles will be heated with stirring to a temperature of about 325-375 C. and reaction will be complete in a period of from about 0.25 to about 3 hours. Usually the sodium treatment will be carried out under nitrogen or under hydrogen, and preferably under hydrogen as this procedure tends to effect a greater reduction in sulfur content. Nitrogen or hydrogen is introduced into the reactor at pressures of from about 500 up to about 1500 p.s.i. The sodium is introduced into the system as a conventional sodium dispersion in a hydrocarbon or ether. Such a dispersion is readily made by vigorous agitation of sodium pieces in white oil or a white oil and resid mixture (about 60% white oil by weight) to effect suitable reduction of the particle size of the sodium. It is preferred to use an amount of sodium in the process of the invention which is at least about 1.5 times that theoretically required to form Na S from the sulfur in the resid. Thus for each gram of sulfur in grams of resid at least about 2.16 grams of sodium will be added.

For the second step of the process, the sodium treated resid material from the first step is cooled and then washed in an aqueous system and in the presence of CO at a temperature of about 250 C. Preferably an amount of water will be used so that for each 200 parts by weight of resid about 300 parts by weight of water is added.

The washing step under pressure of CO need not be carried out for a time more than about one to two hours.

The third step of the process is carried out on the water treated material from the second step. The water is first separated, generally by allowing it to settle at 300 to 400 F., the settled water drawn 0E, and essentially complete removal achieved by vacuum distilling off any remaining water at 100 C. Then, the cooled aqueous material is treated with a lower aliphatic hydrocarbon such as propane, butane, pentane, hexane, and the like, preferably pentane, in a deasphalting technique. Such deasphalting processes are well known in the art; see, for example, Petroleum Processing Handbook, Bland and Davidson, McGraw-Hill, 1967. In carrying out this hydrocarbon extraction, the hydrocarbon from the water-CO wash step is heated under hydrocarbon reflux for a short time to ensure complete extraction of the hydrocarbon soluble material which is the desulfurized and demetallized resid. This reflux usually requires about 0.5 to 2 hours. The hydrocarbon is then stripped from the resid by distil lation and the residual oil remaining is ready for immediate use in a coking operation.

Coking is carried out in the usual manner by drum coking, fluid coking, or by the method of U.S. Pat. 2,709,676 (R. W. Krebs, assigned to Esso Research and Engineering, issued May 31, 1955) to produce coke agglomerates.

The resultant coke material is immediately useful for formation into electrodes or other useful forms where high grade coke is used.

The following example indicates the eflectiveness of the process with respect to the treatment of Lagomedio crude bottoms.

Example A dispersion of sodium was made by vigorous mixing in a counter-rotating blender and at 250 F. for one hour, 40 g. of sodium pieces and a mixture of 54 g. of white oil and 6 g. of a Lagomedio bottoms resid. Measurement of the sodium particle size after treatment indicated the particle size to be below microns.

A Lagomedio bottoms resid (100 g., containing 2.8 g. S) and g. of the above sodium dispersion was placed in an autoclave and mixed thoroughly for one hour at 350 C. and at a hydrogen pressure of 500 p.s.i.g. The sodium treated material was then washed with water and CO at 250 C. for one hour, using 300 g. of water and 24 g. of CO for each 200 g. of treated bottoms. Then the washed bottoms were pentane deasphalted to yield the purified resid product.

The following table illustrates the effectiveness of the above process in removing sulfur, nickel, and vanadium:

TAB LE Material Ni, p.p.m. V, ppm.

S, percent The sulfur and metals free resid as prepared above is subjected to fluid coking (as in US. Pat. 2,881,130) to obtain a metallurgical coke eminently suitable for formation into electrodes.

The invention claimed is:

1. A process for producing electrode grade coke from high sulfur and metal containing hydrocarbon resids comprising the steps of (1) heating the resid at 325-375 C. in the presence of :finely divided sodium and under nitrogen or hydrogen pressure of about 1500 p.s.i.g. for 1-3 hours, (2) washing the sodium treated material with water and CO at elevated temperature, (3) deasphalting the washed material by an aliphatic hydrocarbon extraction to yield a petroleum fraction low in sulfur and metals, and (4) coking said petroleum fraction to obtain an electrode grade coke.

2. A process for producing electrode grade coke from high sulfur and metal containing hydrocarbon resids comprising the steps of (1) heating the resid at 325-375 C. in the presence of finely divided sodium and under nitrogen or hydrogen pressure of about 500 to about 1500 p.s.i.g. for 1-3 hours, the amount of sodium being at least about 1.5 times the theoretical amount required to convert the sodium in said resid to Na s, (2) washing the sodium treated material with water and CO at elevated temperature, (3) deasphalting the washed material by an aliphatic hydrocarbon extraction to yield apetroleum fraction low in sulfur and metals, and (4) coking said petroleum fraction to obtain an electrode grade coke. I

3. The process of claim 1 where step (3) is carried out with pentane.

4. The process of claim 2 where step (1) is carried out in the presence of hydrogen.

References Cited UNITED STATES PATENTS DELBEJRT E. GA-NTZ, Primary Examiner S. L. BERGER, Assistant Examiner US. Cl. X.'R. 

